In this study, we investigated the moderating effect of three set of situational strength variables (group norm, group cohesiveness, and procedural justice climate) on the relationship between Big Five personality Traits and OCB. The situational strength was operationalized as both the mean and the variance of team situational characteristics. Survey data was collected from a final sample set of 62 leaders and 263 team members in 62 teams. Hierarchical Linear Modeling (HLM) analysis showed that the variance of team situational characteristics demonstrated a significant moderating effect, while the mean level of team situational characteristics did not. The strength of group injunctive norm, group cohesiveness, and procedural justice climate moderated the relationship between agreeableness and OCB. The stronger the situation, the weaker is the personality-OCB relation.